Having some trouble on a friends 406. His heater fan controls are not working. I've narrowed it down to no supply to the modulator unit and in turn found out that the fuse that supplies the modulator is not getting any supply, and the fuse is ok.

So my question is, what feeds the fuse? Does it come from another fuse/relay?

Thanks

Had same problem 3yrs ago with mine? ended up taking it to our local car electronics centre cost am arm and a leg as most of the wiring had to be replaced,
sorry this isnt any help, hope you have better luck than l did

Sorry, l have little experience with the 406.
But after reading the first answer, l would hate to see you spend ''an arm and a leg'' on new wiring.

Could you just ADD your own 12 volt feed wire to the modulator and put another fuse in the line. And hide everything behind the dashboard? Total cost, one pound.

What else does not work on the same fuse as the heater fan?

make sure it has a decent earth!
this is very common on electrical faults in cars

There are two fuse ''boxes'' on the 406. One of them is in the engine compartment next to the battery. Its got to be worth checking these fuses one by one as several of them are related to the blower fan and aircon.